Machine for spray coating irregular shapes

ABSTRACT

A machine for spray coating a rotating irregular shape which moves a spray coating device in three paths to provide constant relative speed; standoff distance; and angular relationship between the spray coating device and surface of the shape to be coated.

United States Patent [191 Pelton Oct. 28, 1975 1 1 MACHINE FOR SPRAY COATING IRREGULAR SHAPES [75] Inventor:

John Franklin Pelton, Yorktown Heights, N.Y.

[73] Assignee: Union Carbide Corporation, New

[22] Filed:

York, N.Y.

July 10, 1974 [21] Appl. No.2 487,191

[52] US. Cl. 118/8 [51] Int. Cl. BOSC 13/02 [58] Field of Search 118/8, 2, 75

[56] References Cited UNITED STATES PATENTS 2/1964 Wampler 118/8 X X direction Gauvin 118/8 3,596,632 8/1971 3,709,190 l/l973 Von Gottberg 118/8 X 3,802,911 4/1974 LaCamera i. 118/8 X Primary ExaminerNi1e C. Byers, Jr. Attorney, Agent, or Firm-D. J. Terminello 57 ABSTRACT A machine for spray coating a rotating irregular shape which moves a spray coating device in three paths to provide constant relative speed; standoff distance; and angular relationship between the spray coating device and surface of the shape to be coated.

2 Claims, 8 Drawing Figures Y direction L I Lpi P 8 P U.S. Patent Oct. 28, 1975' Sheet 2 of2 3,915,114

. Q-L/ P76. 20

MACHINE FOR SPRAY COATING IRREGULAR SHAPES This invention relates to a machine for spray coating substrates and more particularly to such a machine for coating irregular shapes whereby a coating of uniform thickness and quality is obtained.

When a round cylindrical part is to be coated by a spray process, such as the plasma spray process, the part is rotated on its own axis at constant speed, the spray device is positioned a fixed distance away and aimed so that the spray strikes the surface at about a 90 angle and the spray device is moved at a constant speed in a direction parallel to the axis of rotation of the part. This simple arrangement provides the four conditions that are necessary for the application of a coating of uniform thickness and quality. These are: (1) constant speed of the part surface past the spray de vice, (2) constant distance between the work surface and the spray device (standoff), (3) constant angle (preferably 90) between the surface to be coated and the direction of travel of the spray particles (impingement angle) and, (4) constant rate of travel of the spray device in the part axis direction. However, when the cylindrical part to be coated is not round, such as in the case of a rotary combustion engine housing, this arrangement fails to hold constant the first three parameters above. It is therefore necessary to provide some other motions.

In the past, variations in part surface speed, because of varying radii with the above arrangement, has been partially compensated for by rotating at a speed that varied through some repetitive cycle during each revolution. The relatively large rotational mass of many parts of interest, combined with the high rotational acceleration required, resulted in the generation of very large inertial forces in the rotating mechanism. This made such equipment difficult to construct or resulted in rapid wear-out and high maintenance costs. If the variation in the part to spray device distance was also compensated for by moving the entire part relative to the spray device, then the above problem was compounded.

Additionally, the angle of the spray device relative to the part surface was not held constant, but the spray device was held in a fixed position.

These existing devices were difficult to construct, difficult to maintain, and did not do a very good job of providing uniform coating thickness and quality.

The main object of this invention is to provide a machine that will produce uniform coating thicknesses on irregular shapes.

Another object is to provide such a machine that is relatively easy to construct and maintain.

Yet another object is to provide a machine for producing a uniform coating thickness on trochoid combustion engine housing using a plasma spray device.

These and other objects will either be pointed out or become apparent from the following disclosure and drawings wherein;

FIG. I is a schematic drawing in elevation illustrating the principles of the invention;

FIG. la is a side elevation partially in cross-sections of the apparatus shown in FIG. 1;

FIGS. 2a through f are diagrams of a trochoid housing in various positions during rotation, showing the angular relationship of the spraying device relative to the surface to be coated.

The above objects are achieved in a general way by rotating the part to be coated at a constant speed about its axis of symmetry (or an axis closest to being an axis of symmetry) and by compensating for variations in surface speed, standoff distances and impingement angle by moving the relatively light-weight spraying device. Variations in part surface speed are compensated for by moving the spray device parallel to-the direction of surface motion either in the same direction or in the opposite direction as required. Variations in standoff are compensated for by moving the spray device in a radial direction. Variations in impingement angle are compensated for by rotating the spraying device about an axis parallel to the part rotation axis.

In a more specific way, the objects are achieved by a machine for metal spray coating irregular shapes which includes in combination with a fixture for receiving irregular shapes to be coated; means for rotating said fixture and shape about an axis in the Z-direction; and means for moving said fixture and shape linearly in the direction of the axis of rotation of the shape, a base; a support system mounted on the base and capable of providing movement in the X and Y direction; a spray device pivotally secured to said support system and located adjacent the shape to be coated so as to deposit coating material on the surface thereof and being movable in the X and Y direction. relative to the surface to be coated in response to movement of said support system; means correlated to the configuration of the shape for moving the support system in the X and Y direction as said shape rotates, thereby maintaining a constant relative speed and a constant distance between the spray device and the surface of the rotating shape; a drive system attached to the spray device to provide arcuate movement of the spray device about the point where the spray device is secured to the support system; means correlated to the configuration of the shape for moving the drive system and thus the spray device so as to maintain a substantially angle of impingement between the coating sprayed from the spray device and the surface of the shape to be coated.

Referring now to the drawings, a typical machine for practicing the invention is shown generally at M in FIG. 1. The machine shown embodies the principals of the invention as they would be employed to construct a machine for coating trochoid engine housings H. The engine housing H is subject to two motions. The first motion is rotational as designated by w. The housing is rotated at a constant angular velocity about an axis through point 0 which corresponds to the axis of the housing. The second motion is linear in the Z-direction as indicated by the arrow in FIG. la so as to maintain a constant rate of travel past the spray device or torch D in this case in the housings axial direction.

To apply an even coating onto the surface of the engine housing, it is important to maintain a constant relative velocity between the torch D and the housing wall W. Since the housing H is rotating at a constant angular velocity, a change in the radius of the housing surface will result in a change of tangential velocity at the housing wall. This variation can be compensated by either moving the torch with or against the motion of the housing surface, i.e., as the radius of the housing increases, the tangential velocity increases and it is necessary to move the torch in the direction of housing surface travel in order to reduce the relative speed. As the radius of the housing decreases, the tangential velocity decreases and it is necessary to move the torch opposite the direction of housing surface travel in order to increase the relative speed. This is accomplished by means of cam C and Links L L L and L By means of the four-bar linkage L L L and L, pivoted about P cam C 3 causes motion in link L, which causes the torch to either move with or against the direction of motion of the housing surface. Thus, a constant surface speed is maintainable between the torch and the engine housing wall. Cam C makes two revolutions to one of the housing, since this housing has a two-fold symmetry.

It is desirable to maintain a constant distance between the nozzle N of the torch and the engine housing. This distance is referred to as standoff. It can be seen in the drawing that as the engine housing is rotated about point standoff would increase from point B to point A, if the torch remained in a fixed position. To compensate for the change in radius from R to R (B to A), torch is connected to a four-bar linkage (links L L L and L pivoted about point P Motion is produced in link L by means of cam C The cam is so constructed as to maintain constant standoff. It should be noted that due to the two-fold symmetry of the engine housing, the cam C, makes two revolutions for a single revolution of the housing.

During the coating process, it is desirable to maintain a 90 impingement angle, i.e., the coating spray should strike the surface of the engine housing at an angle of 90. FIG. 2 shows the desired relation of the centerlines of links L and L at six points during one-quarter of the trochoids revolution about 0. Angles (b, through 4),, indicate the motion of link L during the rotation of the housing. The magnitude of these angles increases from zero for d), to a maximum value near (b then decreases to a zero value for (11 As the trochoid continues to revolve in the next quarter revolution, the value of the angles will be the same for each step of the sequence with the sequence being reversed and the torch inclination being on the opposite side of the center line. FIG. 1 shows that through the action of cam C link L pivots about point P causing motion in link L which in turn causes an angular displacement in link L which is pivoted about point P Thus, by the angular displacement of link L the 90 impingement angle can be maintained as the housing is rotated. It should also be noted that for two revolutions of cam C the engine housing makes only one revolution due to the two-fold symmetry of the housing.

It is important to note that the axis about which the torch is rotated (through point P must be coincident with the surface to be coated. It is important because that is the only relationship which will allow angular displacement of the torch centerline without causing the impingement point to move on the housing surface.

By using this configuration, angular torch disposition can be plotted without giving consideration to secondary effects.

It is obvious that the motion produced by cam C in order to maintain constant surface speed, has a direct interaction with the angular torch position. If links L and L are exactly the same length, then cam C can be made the same shape as cam C and with proper synchronization there will be no angular motion of L relative to L The angular motion then becomes a product of the deviations in the shape of cam C from that of cam C It is also obvious that the motions described are not perfectly linear but, in fact, curve linear. If the lengths of the various linkage members are chosen sufficiently long, the motions can be treated as linear.

While the invention has been described with reference to certain preferred embodiments, it should be understood that the principles of the invention can be applied to various modifications without departing from the spirit and scope of the invention. For example, the spraying device could be any kind of metal spraying torch, i.e., electric or oxy-fuel gas flame. The part to be coated could be any irregular shape, for example, elyptical, egg shaped, etc. The support mechanism for moving the coating device could be typical machine cross slides together with a torch rotating device. The motions that are produced by cams could be produced by tape, computer or other electronically controlled moving device. The cams themselves need not be designed to make two revolutions for one revolution of the housing. Such design is used in the preferred embodiment for reasons of simplified construction.

It should be further understood that while in the embodiments shown and described the fixture and shape are provided with motion in the Zdirection relative to the base, the same effect can be obtained by moving the torch support system in the Z direction relative to the base.

What is claimed is:

l. A machine for spray coating of irregular shapes wherein relative motion is provided between said irregular shapes and said machine in the X, Y and Z- direction, comprising the combination of a fixture for receiving an irregular shape to be coated, means operatively related to said fixture for rotating said fixture and shape about an axis in the Z-direction and means operatively related to said fixture for moving said fixture and shape linearly in the direction of the axis of rotation of said shape; with base; a support system mounted on said base and capable of providing movement in the X and Y directions', a spray device pivotally secured to said support system and located adjacent said shape to be coated so as to deposit coating material on the surface thereof and being movable in the X and Y direction relative to the surface to be coated in response to movement of said support system; means correlated to the configuration of said shape for moving the support system in the X and Y direction as said shape rotates thereby maintaining a constant relative speed and a constant distance between the spray device and the surface of said rotating shape, a drive system attached to said spray device to provide arcuate movement of said spray device about the pivotal point where said spray device is secured to said support system; means correlated to the configuration of said shape for moving said drive system and thus said spray device in an arcuate path so as to maintain a substantially angle of impingement between the coating material sprayed from said spray device and the surface of the shape to be coated.

2. A machine for spray coating of irregular shapes wherein relative motion is provided between said irregular shapes and said machine in the X, Y and Z- directions, comprising in combination a fixture supporting the irregular shape to be coated;

means operatively related to said fixture and for rotating said fixture and said shape and means operatively related to said fixture for moving said fixture and shape linearly in the direction of the axis of rotation said fixture, and

' base, a four bar linkage pivotally mounted to said base with each of said four bars being pivoted to each other to form a parallelogram linkage, a metal spraying device pivotally mounted to said four bar linkage at a point diagonally opposite the point where said four bar linkage is pivotally mounted to said base and positioned relative to said fixture and shape so as to deposit coating material onto said shape, means associated with the four bar linkage and correlated to the shape to be coated for causing motion of said spray device relative to the rotational motion of said shape so as to maintain a constant relative speed between the spraying device and the rotating shape, means associated with the four bar linkage and correlated with the shape to be coated for moving said spraying device to and from the surface of said rotating shape to maintain a constant distance between said spraying device and the surface of said rotating shape regardless of changes in contour of said surface, a second linkage means pivotally mounted on said base and connected to said spraying device to cause angular motion of said spraying device relative to said rotating surface, means correlated with the shape to be coated and to the means for maintaining constant distance between the spraying device and surface for moving said second linkage means.

l= l l= l 

1. A machine for spray coating of irregular shapes wherein relative motion is provided between said irregular shapes and said machine in the X, Y and Z-direction, comprising the combination of a fixture for receiving an irregular shape to be coated, means operatively related to said fixture for rotating said fixture and shape about an axis in the Z-direction and means operatively related to said fixture for moving said fixture and shape linearly in the direction of the axis of rotation of said shape; with a base; a support system mounted on said base and capable of providing movement in the X and Y directions; a spray device pivotally secured to said support system and located adjacent said shape to be coated so as to deposit coating material on the surface thereof and being movable in the X and Y direction relative to the surface to be coated in response to movement of said support system; means correlated to the configuration of said shape for moving the support system in the X and Y direction as said shape rotates thereby maintaining a constant relative speed and a constant distance between the spray device and the surface of said rotating shape, a drive system attached to said spray device to provide arcuate movement of said spray device about the pivotal point where said spray device is secured to said support system; means correlated to the configuration of said shape for moving said drive system and thus said spray device in an arcuate path so as to maintain a substantially 90* angle of impingement between the coating material sprayed from said spray device and the surface of the shape to be coated.
 2. A machine for spray coating of irregular shapes wherein relative motion is provided between said irregular shapes and said machine in the X, Y and Z-directions, comprising in combination a fixture supporting the irregular shape to be coated; means operatively related to said fixture and for rotating said fixture and said shape and means operatively related to said fixture for moving said fixture and shape linearly in the direction of the axis of rotation said fixture, and a base, a four bar linkage pivotally mounted to said base with each of said four bars being pivoted to each other to form a parallelogram linkage, a metal spraying device pivotally mounted to said four bar linkage at a point diagonally opposite the point where said four bar linkage is pivotally mounted to said base and positioned relative to said fixture and shape so as to deposit coating material onto said shape, means associated with the four bar linkage and correlated to the shape to be coated for causing motion of said spray device relative to the rotational motion of said shape so as to maintain a constant relative speed between the spraying device and the rotating shape, means asSociated with the four bar linkage and correlated with the shape to be coated for moving said spraying device to and from the surface of said rotating shape to maintain a constant distance between said spraying device and the surface of said rotating shape regardless of changes in contour of said surface, a second linkage means pivotally mounted on said base and connected to said spraying device to cause angular motion of said spraying device relative to said rotating surface, means correlated with the shape to be coated and to the means for maintaining constant distance between the spraying device and surface for moving said second linkage means. 